Loading area of 13-15 or more RM (high repetition range): aims to maximize local muscular resistance.

While these guidelines are generally accepted as principles , their application to the design of the training program remains somewhat misleading.

As I have just commented, most of the scientific evidence seems to suggest the presence of a continuum of strength-resistance, whereby low repetition training with heavy loads (1-5 RM) induces a maximum increase in force while the light load and high repetition training (13-15 or more RM) promote greater increases in muscle endurance.

However, with respect to the growth of skeletal muscle, that is, if we talk about muscle mass gains (hypertrophy) , the scientific evidence does not show a hypertrophic superiority of one loading area in comparison with another in both untrained people and trained people.

That is, there are studies that have found similar long-term increases in muscle size in subjects who trained strength by performing series in low and medium ranges of repetitions (3-10 RM) and in subjects who trained by performing series in high ranges of repetitions (10-30 RM), whenever muscle failure is reached.

Does this mean that it does not matter the load (number of repetitions) when it comes to gaining muscle mass while we reach muscle failure ?

Coming to muscle failure, the burden of strength exercise does not seem to determine muscle mass gains

Well, it seems that yes. The scientific evidence suggests that, while reaching the muscle failure, the load is not determinative , and similar gains muscle training may occur in different ranges of repetitions.

That is to say, that people who train always in ranges of 8-10 repetitions can have similar increases of the muscular mass that people who train in ranges of 15-20 repetitions, for example, whenever these arrive at the muscular failure in the series of the different exercises.

This, in part, is positive news, since it means that different ranges of repetitions , while we reach muscle failure , can lead us to achieve the intended goal of gaining muscle mass.

Therefore, good news is that if we want to gain muscle mass we can train in different ranges of repetitions and we can choose the range in which we feel more comfortable or more we like (yes, the hypertrophy is quite grateful).

But here doubts continue to arise. We know that always arriving at muscle failure is not appropriate , since negative effects can occur:

Production of excessive fatigue and muscle damage ( stiffness ) and, consequently, a worse recovery for the performance of the following exercises and for the following training sessions in the following days.

Possible deterioration of the technique in the last repetitions , with the consequent risk of injury, among other effects.

In turn, we must ask ourselves: is it always necessary to reach muscle failure to gain muscle mass?

The scientific evidence mentioned above is based on studies in which subjects arrive at muscle failure in training, and the conclusions are the exposed ones (similar gains of muscle mass in different ranges of repetitions).

But there is also a lot of scientific evidence that says you can get similar increases in muscle mass by keeping some repetitions in the reserve (repetitions that we can perform but do not perform) that reaching muscle failure.

For example, with a weight with which we can perform 10 maximum repetitions we perform 8 repetitions and stop (we keep two repetitions without performing in the bedroom).

Even so, if we want to maximize muscle mass gains and provoke a greater stimulus we must be close to this muscle failure (keep one or two repetitions before reaching muscle failure).

But this does not end here, and understanding the role of muscle fibers can be a key point in the process of gaining muscle mass.

The type II muscle fibers have speeds faster and shortening the ability to generate more force than the type I muscle fibers

Alternatively, in comparison with type II fibers, type I muscle fibers have a greater oxidative capacity (greater capacity to use oxygen) and a higher fatigue threshold (they take longer to fatigue).

Both type I fibers and type II fibers have the ability to hypertrophy .

However, research shows that the growth capacity of type II fibers is approximately 50% greater than that of type I fibers, although a high degree of interindividual variability is observed with respect to the degree of hypertrophic adaptation.

Making a small note here, we must bear in mind that sex, age and training history influence many aspects of the responses that lead to muscle mass gain (not all of us gain muscle mass in the same way, aa same speed or the same amount).

Following the role of muscle fibers and based on the information given, it can be assumed that the recruitment of type II fibers should be the main focus of the design of the exercise program for the increase of muscle mass, given the higher rate of hypertrophy in these fibers compared to type I fibers.

Despite this logical reasoning, emerging evidence suggests that such an approach may be simplistic and perhaps wrong , at least if the goal is to maximize muscle size.

Type I (slow) fibers may also play an important role in muscle hypertrophy

An emerging body of evidence is beginning to suggest that hypertrophy of skeletal muscle fibers may be load-specific , and that type I (slow) fibers also have a good ability to hypertrophy.

In other words, it may be that strength training with high loads (ie ≥60% 1RM = medium and high loads) emphasize further growth of type II muscle fibers , while the strength training with low loads (is say, <60% of 1RM = low loads) could increase mainly the hypertrophy of type I muscle fibers .

Due to the lower fatigability of type I muscle fibers, it can be assumed that a longer loading time is necessary to stimulate an accentuated growth of these fibers, being able to achieve an increase in time under load when training with lower loads (for example , 30% of 1RM = high repetitions) and muscle failure .

It can be hypothesized that a different stimulus may be needed to elicit a maximum hypertrophic response in different types of muscle fibers due to the nature of their machinery.

Recent evidence seems to support this hypothesis (although more should be investigated), pointing towards the preferential hypertrophy of type I muscle fibers when strength training is carried out with low loads (13-15 or more repetitions) to muscle failure.

Applying all this to our workouts

A lot of theory, but how do I apply all this in my workouts?

I’m going to divide it into two key points to make it clearer:

1. Varies the ranges of repetitions

If your goal is simply to maximize overall muscle mass, your exercise prescription should include training in a wide range of repetition ranges .

The exercise of greater intensity (≥60% of 1RM = medium and high loads) seems necessary to fully stimulate the growth of fibers of fast contraction (type II), while the exercise of less intensity (<60% of 1RM = low loads ) improves preferentially hypertrophy in slow-twitch fibers (type I).

A periodized approach in which you combine high and low intensity trainingcan help you ensure an optimal hypertrophic response across the continuum of fiber types.

In turn, as recent studies indicate , it is more interesting to use interesting variable load schemes in which the ranges of repetitions are alternated throughout the training program.

This type of schemes can provide comparable adaptations to always work with the same repetition range (example: I always work at 8-12 repetitions) with a reduced volume load (same results but with less amount of work).

This indicates a more efficient training stimulus compared to training exclusively in a fixed repetition range.

2. Loads, exercises and muscular failure

Train with a head We use high loads (1-5 reps) and medium-high (6-10 reps) in multi – joint exercises like chin , deadlift , squat , military press, bench press , pendlay rowing, etc., at the beginning of our session.

In these exercises we will work a lot of musculature and, being highly technical exercises that require great control and coordination , much less will be the exercises in which we reach muscle failure.

These exercises will be those in which we will leave those repetitions in the reserve (1-2 repetitions or more without realizing) that I mentioned in previous points and in which we will incide more in the hypertrophy of the type II fibers (fast) , which are the ones that have more capacity for hypertrophy.

We use medium-low (10-12 repetitions) and low (13 or more repetitions) loads in monoarticular or isolation exercises such as pulley crossings for pectorals , biceps curls and variants, lateral shoulder lifts , triceps extensions on the pulley and variants , exercises in a guided machine that requires less body control, etc., preferably at the end of our session.

In these exercises we can get closer to muscle failure or even to muscle failurefrom time to time and will be those that will influence more on the hypertrophy of type I fibers (slow) , which as we have seen may have an important role in hypertrophy muscular.

As a point, it is not necessary that in each training we use exercises with high loads at the beginning and low loads at the end.

Maybe in a workout we only use high and medium loads and dedicate another training to work with low loads. The combination of repetition ranges in your sessions or your training microcycles can be done in different ways.

Apply these tips based on science. The combinations may be different, but always train with a head .